1. Field of the Invention
The invention relates to the field of thin films deposited on a substrate, it relates more particularly to the deposition of thin films, of black film type, and in particular Newton black films (NBF).
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
Black films correspond to a state of equilibrium of a surface active film, a so-called free film, which is generally obtained after draining the solvent it contains. Their structure is generally determined by X-reflectivity, which gives access to the thicknesses, rugosities and density of the different strata of this nanometric film. Two types of black film are differentiated: the common black film (CBF) and the Newton black film (NBF). These films are often studied after formation from a surface active solution in water. Unlike biological membranes, in black films, the polar heads of the surface active bilayer are in contact whereas the aliphatic chains are not, indeed the external medium corresponds to an aqueous medium in the former case whereas in the latter it is generally a gaseous atmosphere substantially close to ambient air.
The common black film corresponds to a metastable state of the film which still contains water molecules in liquid state. This type of film may lead to the formation of a Newton black film by evaporation of the liquid water.
The Newton black film is formed of two surface active walls, bonded to one another, without liquid water. The presence of water in the film is nevertheless detected but it corresponds to molecules trapped solid inside the film and which partake to the cohesion thereof. These molecules are not free and are not liable to leave the film inasmuch as the former does not undergo any extreme treatment. The loss of these water molecules is often synonymous with destruction of the film.
It has been shown that the Newton black films form a model system perfectly organized for studying interactions in quite various physicochemical systems (surfactants, polymers, proteins). Thus for instance, a layer of proteins and of modified cyclodextrins has already been inserted inside a black film.
The black films, in spite of the degree of organization that some of them may exhibit, are extremely brittle. Thus, the simplest interferences may lead to the rupture thereof when they are studied according to conventional methods. This brittleness also makes it impossible to find industrially viable applications for this type of structure.
Thanks to the present invention, the inventors provide a simple and smart reply to the brittleness of black films which besides paves the way for numerous applications.